Twenty Seventeen has a similar social media iconset included, and has received similar requests: #43342, #45328

I don't see an issue with adding these ones (especially the ones that have patches already), but I will note that we should probably agree on some limitations around these sorts of additions: there are a near-infinite number of social media services out there, and we won't be able to include them all. In addition, each icon added provides a (admittedly very tiny) file size bump, and as these services update their logos over time, there'll be maintenance required to keep these up to date.